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Posted By Topic: Main Earth and Mains Neutral on same stud

OctaneOutlaw
Oct 26 2019 07:35

I've seen a few switchboards where the MEC and main incoming neutral conductor are on the same stud

These boards do not just have one bar for neutral and earth like some old ones do

They have an earth bar, MEN link and neutral bar

Both the main earth and incoming neutral are on the same stud on the neutral bar

Was this something that used to be ok? If I work on such a board at what point, if any, should I remedy this and move the MEC to the earth bar or should I just be leaving it as is as it?
   

AlecK
Oct 26 2019 09:06

Under 1976 Regs, that was the required configuration.
You'll find older DBs & caravans set up the same way.
Under those rules, the connection had to be by nut & locknut

ESR 113 says it's OK to remain in service, ie the "no mandatory upgrade" principle that's almost universal in NZ law.

For a MSB, changing it doesn't make any difference to safety performance of the MEN system - which is what the N-E connection is about. But it does alter how we have to go about some kinds of testing.

For DBs & caravans, that config means the submain (supply lead) N & PEC are effectively in parallel; so the PEC will be carrying load current - which is not permitted for installations done to today's rules.
Also where there's multiple N-E connections, they ALL have to be found and opened when doing testing.
That's why we no longer use that configuration.



   

falcon5nz
Nov 13 2019 13:09

To my interpretation ofAS/NZS 3019 4.3(f)

"Where there are separate earth and neutral bars, earthing conductors are connected to the
earth bar and neutral conductors are connected to the neutral bar"

it would fail a Section 4 periodic verification which is what some of the insurers seem to be requiring.

That opinion is worth exactly what you paid for it though
   

Sarmajor
Nov 13 2019 13:25

No it wouldn’t fail anything. It was compliant when it was installed and remains compliant.

All periodic verifications must be carried out using the rules that applied when the installation or part installation was first livened.

The section of the rules that you have quoted refers to me work only..
   

falcon5nz
Nov 13 2019 14:12

The section I have quoted refers to Verification by visual inspection and limited testing, specifically Inspection of switchboards.

I realise if it complied when it was built it complies now, but why does it reference "...separate earth and neutral bars..."? Is that intended to be for submains where the bars are electrically and physically seperate?
   

AlecK
Nov 13 2019 16:42

I believe it's to distinguish between the separate bars we have now, and the older set-up with a single bar for both Ns & Es.

But you've highlighted a glitch, in that it needs to be amended to permit older MECs(earthing leads as it used to be) to remain on the N.

The revision of 3019 is under way now; so your timing is excellent

   

BrianW
Nov 15 2019 15:46

It also highlights another problem.

If there's no 'date of installation' on the switchboard, which is highly unlikely on anything from 1976 to 2000 or more, how is any young sparky with just a few years experience under their belt expected to know what set of rules the installation complies with?

Given that there are few clues on a later installation, pre rule change, that differentiate it from a post rule change era, it makes it purely a guessing game in many cases.

Without researching right now, i'm unsure exactly when that changed, but i got tripped up with exactly that during a switchboard change not that many years ago. Earth and Neutral under the same stud, only to be told by the inspector that we don't do it that way anymore.
   

OctaneOutlaw
Nov 15 2019 18:46

This is exactly my problem as someone who has recently gained registration and only has 3-4 years electrical experience I just take the time to ask these questions because otherwise I'd have no idea

I know we can track down older documents that used to be used but like you say it's a matter of knowing what one was worked to and even then it can still be hard to find the relevant information

Making sure our work is done correctly and having a decent knowledge of current standards is hard enough for some let alone being familiar with older ones
   

DougP
Nov 15 2019 19:13

For " a switchboard change not that many years ago" you would do it to the current rules. It doesn't really matter when the original switchboard was installed.

As for knowing approximate dates - the use of solid green earth in TPS might be a clue (but don't ask me when that changed to green/yellow).

But in any case, pretty much all work that you do needs to be done to current standards other than just replacement of fittings.

And while replacing a switchboard might just be a replacement of a whole lot of fittings, you wouldn't do the work to the 1960 methods just because that's the age of the installation.
   

pluto
Nov 15 2019 21:38

If replacing the distribution switchboard, or or wanting to remove the MEN link and the existing submain active and neutral conductors are protected by a overcurrent device of the correct rating.

If the protective earth core was too small in accordance with AS/NZS 3000, running of a new correctly sized protective earth conductor is satisfactory, just follow the existing submain route beck to the main switchboard and connect the ends of the new cable to the earth bars of main and distribution switchboards and don't fit the MEN link in the distribution switchboard.


   

SymonS
Nov 15 2019 22:43

Pluto, What the f#$k are you on !!

How is your comment in any way relevant to the original question ??

DougP. That would depend entirely on how many years ago BrianW was referring too, but as usual, the condescending self righteous have chimed in.

It seems to me that the point being made is that there simply isnt enough information made available to younger sparkys for them to be expected to make decisions around older installations, and I agree with him.
   

DougP
Nov 16 2019 13:18

SymonS - there's 20 years worth of standards available in PDF for free on Standards NZ website. And there's older ones available from other sources as well.

Presumably the "younger sparkys" have also done an apprenticeship where they should have received some guidance from their tradesman on the requirements.

From what I've seen and discussed hundreds of times with other tradesmen here and in Australia, it's simply their own laziness that limits their knowledge.
   

daniel2
Nov 16 2019 13:45

BrianW
Nov 15 2019 15:46

It also highlights another problem.

If there's no 'date of installation' on the switchboard, which is highly unlikely on anything from 1976 to 2000 or more, how is any young sparky with just a few years experience under their belt expected to know what set of rules the installation complies with?

Given that there are few clues on a later installation, pre rule change, that differentiate it from a post rule change era, it makes it purely a guessing game in many cases.

Without researching right now, i'm unsure exactly when that changed, but i got tripped up with exactly that during a switchboard change not that many years ago. Earth and Neutral under the same stud, only to be told by the inspector that we don't do it that way anymore.“

Going a little off topic, but I’ve never heard of this.

I never write the date of installation on a MSB. The indication of a date is given on the COC and ESC.

Inspectors write the date of ‘livening’ on the sticker within the meter box or MSB/meter board.
   

DougP
Nov 16 2019 13:56

daniel2 AS/NZS3000 8.4

   

daniel2
Nov 16 2019 14:43

Yes, as stated in my last post.

Inspection ROI and sticker.

Coc/esc by electrician.




   

AlecK
Nov 17 2019 20:04

FTR,
that sticker has absolutely nothing to do with certification, and almost nothing to do9 with date of livening,
It's the date of certification of the metering required by the rules for energy suppliers, issued & affixed by the metering contractor on behalf of the meter owner.

If the person installing & / or certifying the metering happens to also be an inspector, that's a complete co-incidence.

   

SymonS
Nov 17 2019 20:35

Daniel2. Please enlighten us to where the CoC and/or ROI exist prior to 2000 !? Or are you simply too young to have any clue whatsoever what we were doing from 1976 (and beyond for some of us) to when we were required to produce such documents !

The point made about younger sparkys having little information readily available to them to date an installation, and therefore understand the rules under which it was installed, and the differences to today's rules, for them to make decisions about whats legal or not before they do any work, and as a result, prevent them from performing unnecessary work, is a valid one !
   

daniel2
Nov 17 2019 22:02

SymonS. Please cool it.
   

daniel2
Nov 17 2019 22:03

Sometimes, a date could be found written within the meter box.

   

daniel2
Nov 17 2019 22:31

"
If the person installing & / or certifying the metering happens to also be an inspector, that's a complete coincidence"

Most of the time it is.
   

SymonS
Nov 17 2019 22:59

Daniel2. Go back and read the original post !!

Based on that post, I would suggest that OctaneOutlaw is Not an inspector! Rather, he's a typical young sparky who has little idea about what was legal before he gained registration, and limited options available to him to find out when needing to make quick decisions in the field !
   

daniel2
Nov 18 2019 06:56

SymonS, who said he was an inspector?


   

Andrew
Nov 26 2019 14:37

You can maintain an existing installation in any of the ways listed in ESR59, so if you're unsure you can always go with the current rules. Occasionally this may mean someone else can do it cheaper by installing to the rules of the day, and occasionally the rules of the day will be the only practical way to maintain something, in which case you either take the time to look them up or let someone else do the job.